import java.util.Scanner;

public class Test08 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        int sum = 0;
        for (int i = 1; i <= n; i++) {
            sum+=i*(1+i)/2;
        }
        System.out.println(sum);

    }
}
